575 research outputs found

    Functional Impairment, Illness Burden, and Depressive Symptoms in Older Adults: Does Type of Social Relationship Matter?

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    Objective: The nature of interpersonal relationships, whether supportive or critical, may affect the association between health status and mental health outcomes. We examined the potential moderating effects of social support, as a buffer, and family criticism, as an exacerbating factor, on the association between illness burden, functional impairment and depressive symptoms. Methods: Our sample of 735 older adults, 65 years and older, was recruited from internal and family medicine primary care offices. Trained interviewers administered the Hamilton Rating Scale for Depression, Duke Social Support Inventory, and Family Emotional Involvement and Criticism Scale. Physician-rated assessments of health, including the Karnofsky Performance Status Scale and Cumulative Illness Rating Scale, were also completed. Results: Linear multivariable hierarchical regression results indicate that social interaction was a significant buffer, weakening the association between illness burden and depressive symptoms, whereas perceived social support buffered the relationship between functional impairment and depressive symptoms. Family criticism and instrumental social support were not significant moderators. Conclusions: Type of medical dysfunction, whether illness or impairment, may require different therapeutic and supportive approaches. Enhancement of perceived social support, for those who are impaired, and encouragement of social interactions, for those who are ill, may be important intervention targets for treatment of depressive symptoms in older adult primary care patients

    On the Source of Energetic Electron Precipitation during Auroral Substorms

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    Precipitating auroral electrons are believed to originate mainly from parallel electric fields set up at the auroral acceleration region (AAR) extending up to 20,000 km altitude. However, electrons of energy greater than 100 keV are probably generated by acceleration processes beyond the AAR. Observational evidence for the source location of these energetic electrons are hard to come by. In our current work, we present simultaneous magnetically conjugate measurements of energetic electron spectra estimated at the ionosphere using the Poker Flat Incoherent Scatter Radar (PFISR) and measured at the inner plasma sheet by the THEMIS spacecraft. The flux of precipitating electrons of energy greater than 100 keV demonstrate a striking spatio-temporal correlation with that of the inner plasma sheet electrons. This suggests that the source of the energetic electrons lie at or beyond the inner plasma sheet, and that the acceleration processes within the auroral acceleration zone don't contribute substantially to their energization. Using simultaneous THEMIS measurements of wave power, we speculate that the electromagnetic ion cyclotron (EMIC) and Chorus waves are likely candidates for electron acceleration within the inner plasma sheet apart from the usual candidates of betatron and fermi acceleration. However, between the ionosphere and the plasma sheet, electrons of energy less than 100 keV show significant differences in their energy spectra after the substorm onset suggesting an active AAR

    Reconstruction of Fine Scale Auroral Dynamics

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    We present a feasibility study for a high frame rate, short baseline auroral tomographic imaging system useful for estimating parametric variations in the precipitating electron number flux spectrum of dynamic auroral events. Of particular interest are auroral substorms, characterized by spatial variations of order 100 m and temporal variations of order 10 ms. These scales are thought to be produced by dispersive Alfvén waves in the near-Earth magnetosphere. The auroral tomography system characterized in this paper reconstructs the auroral volume emission rate to estimate the characteristic energy and location in the direction perpendicular to the geomagnetic field of peak electron precipitation flux using a distributed network of precisely synchronized ground-based cameras. As the observing baseline decreases, the tomographic inverse problem becomes highly ill-conditioned; as the sampling rate increases, the signal-to-noise ratio degrades and synchronization requirements become increasingly critical. Our approach to these challenges uses a physics-based auroral model to regularize the poorly-observed vertical dimension. Specifically, the vertical dimension is expanded in a low-dimensional basis consisting of eigenprofiles computed over the range of expected energies in the precipitating electron flux, while the horizontal dimension retains a standard orthogonal pixel basis. Simulation results show typical characteristic energy estimation error less than 30% for a 3 km baseline achievable within the confines of the Poker Flat Research Range, using GPS-synchronized Electron Multiplying CCD cameras with broad-band BG3 optical filters that pass prompt auroral emissions.National Science Foundation Atmosphere and Geospace Directorate, Grants 1216530, 123737

    The California-Kepler Survey V. Peas in a Pod: Planets in a Kepler Multi-planet System are Similar in Size and Regularly Spaced

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    We have established precise planet radii, semimajor axes, incident stellar fluxes, and stellar masses for 909 planets in 355 multi-planet systems discovered by Kepler. In this sample, we find that planets within a single multi-planet system have correlated sizes: each planet is more likely to be the size of its neighbor than a size drawn at random from the distribution of observed planet sizes. In systems with three or more planets, the planets tend to have a regular spacing: the orbital period ratios of adjacent pairs of planets are correlated. Furthermore, the orbital period ratios are smaller in systems with smaller planets, suggesting that the patterns in planet sizes and spacing are linked through formation and/or subsequent orbital dynamics. Yet, we find that essentially no planets have orbital period ratios smaller than 1.21.2, regardless of planet size. Using empirical mass-radius relationships, we estimate the mutual Hill separations of planet pairs. We find that 93%93\% of the planet pairs are at least 10 mutual Hill radii apart, and that a spacing of ∼20\sim20 mutual Hill radii is most common. We also find that when comparing planet sizes, the outer planet is larger in 65±0.4%65 \pm 0.4\% of cases, and the typical ratio of the outer to inner planet size is positively correlated with the temperature difference between the planets. This could be the result of photo-evaporation.Comment: Published in The Astronomical Journal. 15 pages, 17 figure

    The California-Kepler Survey. II. Precise Physical Properties of 2025 Kepler Planets and Their Host Stars

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    We present stellar and planetary properties for 1305 Kepler Objects of Interest (KOIs) hosting 2025 planet candidates observed as part of the California-Kepler Survey. We combine spectroscopic constraints, presented in Paper I, with stellar interior modeling to estimate stellar masses, radii, and ages. Stellar radii are typically constrained to 11%, compared to 40% when only photometric constraints are used. Stellar masses are constrained to 4%, and ages are constrained to 30%. We verify the integrity of the stellar parameters through comparisons with asteroseismic studies and Gaia parallaxes. We also recompute planetary radii for 2025 planet candidates. Because knowledge of planetary radii is often limited by uncertainties in stellar size, we improve the uncertainties in planet radii from typically 42% to 12%. We also leverage improved knowledge of stellar effective temperature to recompute incident stellar fluxes for the planets, now precise to 21%, compared to a factor of two when derived from photometry.Comment: 13 pages, 4 figures, 4 tables, accepted for publication in AJ; full versions of tables 3 and 4 are include
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